With 21st century technology they were pumping millions of tons per day. A couple of cubic kilometres per year, from an aquifer holding over a hundred thousand cubic kilometres of water. The best they could manage in the thirties would be like emptying a swimming pool with a teaspoon and their expectation would likely be that it would last centuries.
For comparison look at the equivalent in the US where no-one even thought about exhaustion or conservation until fairly recently https://en.wikipedia.org/wiki/Ogallala_Aquifer?wprov=sfti1